Machine for routing stair stringers



May 15, 1956 o. PEARSON MACHINE FOR ROUTING STAIR STRINGERS 4 Sheets-Sheet l Filed May 5, 1954 INVENTOR.

NS vv@ NNN Hl Sui" Y @Sl AT TORNEKS` May i5, 1956 o. PEARSON MACHINE FOR ROUTING STIR STRINGERS 4 Sheets-Sheet Filed May 3, 1954 INVENTOR.

TTORNEY5 May 15, 1956 o. PEARSON 2,745,449

MACHINE FOR ROUTING STAIR STRINGERS Filed May 3, 1954 4 Sheets-Sheet 3 /Z 0/1//59 L 609/710 Mai/0A AT TOHNE Y 5 May 15, 1956 o. PEARSON 2,745,449

MACHINE FOR ROUTING STAIR STRINGERS Filed May 5, 1954 4 Sheets-Sheet 4 IN V EN TOR.

ATTORNEYS United States Patent MACHINE FOR ROUTING STAIR STRINGERS Olaf Pearson, West Orange, N. I. Application May 3, 19254, Serial No. 427,187

12 Claims. (Cl. 1441-136) This invention relates to a machine for making Stair stringere. More especially, the invention is concerned with the routing of channels in the face of a stair Stringer for receiving the ends of the n'sers and the treads of a stairway.

It is an object of the invention to provide an improved machine for making Stair stringers, and the improvements are concerned more especially with adjustments whereby the machine can be used for making stringers for staircases having a wide variety of rise-to-run ratios. Staircases are not standardized, and ,the architect for each house makes his own Selections for the height of each step and the depth of the tread of the step. Depending upon these factors and the height of the ceiling in the house, the number of steps and the rise-run ratio are determined. With this invention, it is possible to cut Stringer channels for any selected riserun ratio tha may be called for by the plans of any house.

This invention relates to machines of the class in which the stair Stringer is located under a guide plate having slots through which a router tool extends, and in which the sides of the slots serve as guides for the router tool.

In accordance with one feature of the invention, the mechanism for feeding the stair Stringer, with a stepby-step motion, is provided with an adjustment for correlating the length of the feed steps with the rise-run ratio for which the router guides are Set. Another feature of the invention relates to the control means for operating the feed mechanism and for operating clamps that hold the stair Stringer accurately in position during each routing operation. This control mechanism is constructed for sequential operation so that the feed mechanism and clamping means will operate in the desired relation to one another. Other features relate to a construction for cutting the channels for right and left-hand stringers, for reversing the operation of the feeding mechanism, and for automatically selecting di'lerent clamping means depending upon whether the machine is adjusted for cutting a right or a left-hand Stringer.

Other objects, features and advantages of the invention will appear or be pointed out as thedescription proceeds.

ln the drawing, forming a part hereof, in which like reference characters indicate corresponding parts in all the views:

Figure l is a front elevation of a machine for routing stair stringers in accordance with this invention;

Figure la is a greatly enlarged sectional View through the rack and its support of Fig. 1, the section being taken at the plane lar-1a indicated in Figure l;

Figure 2 is an enlarged sectional view taken on the line 2 2 of Figure l;

Figure 3 is a detailed view of a portion of the mechanism for feeding the holder on which the stair Stringer is carried; Y

Figure 4 is a top view of the feeder mechanism shown in Figure 2;

2,745,449 Patented May l5, 1956 ice Figure 5 is an enlarged, topA plan view of the Stringer routing machine shown in Figure 1;

Figure 6 is a top plan View of one end of the Stringer holder Viewed from the plane 6 6 of Figure 1;

Figure 7 is an enlarged sectional view taken on the line 7-7 of Figure 5;

Figure 8 is an enlarged end View of the Stringer routing machine shown in Figures 1 and 5;

Figure 9 is a greatly enlarged front View of the manually controlled device for controlling the Sequence of operations of the machine;

Figure l() is a sectional view through one of the guide plates showing the way in which a router tool is guided by the edge of the slot through the guide plate;

Figure ll is a diagrammatic View showing the fluid motor by which the feed mechanism is operated and the magnetic valve by which the working uid supply to the motor is controlled; and

Figure 12 is a wiring diagram for the machine shown in the other gures.

The machine shown in Figure 1 includes a main frame 10 with supporting legs 11 which rest upon the floor. The top of the main frame 10 includes longitudinal channels 12, best shown in Figures 5 and 8; and transverse tieplates 13. The space enclosed by the channels 12 and tieplates 13 is open to leave room for router tools to reach the work piece.

On top of the channels 12 and tieplates 13 there are guide plates 16 and 17. These guide plates have slots 21 and 22 through which the cutting tool extends. There are graduations along one side of each of the slots 21 and 22 and these sides of the Slots serve as guide means for router tools that cut the grooves in the stair stringers. The edge of the slot 21 guides the tool for cutting the groove in the Stringer for the tread of the stair, and the slot 22 guides the tool for cutting the groove in the Stringer which receives the riser. y

The guide plate 16 is used for cutting right-hand stringers and the guide plate 17 is used for cutting lefthand stringers. It will be evident, therefore, that for any particular work piece, only one of the guide plates is used to guide the tool. It is an important advantage of the invention, however, that means are provided for simultaneously adjusting the guide plates 16 and 17 for diiferent values and combinations of rise and run distance so that after putting one stair Stringer through the machine, the machine is accurately adjusted to cut the corresponding stringer for the other side with exactly corresponding dimensions.

The guide plates 16 and 17 have slots 25 through which stud bolts 26 extend. These stud bolts are attached to the longitudinal channels 12 and they have nuts 27 at their upper ends for securely clamping the guide plates 16 and 17 to the longitudinal channels 12. When the guide plates 16 and 17 are to be adjusted to make stair stringers with a different rise or run from those of the last Stringer made on the machine, the nuts 27 are loosened so as to leave the guide plates 16 and 17 free to move on the top faces of the channels 12. The slots 2S are arcuate slots with centers of curvature at axes 29. The guide plate 16 is provided with a bearing on which it rotates about one of the axes 29 as a center. This construction is Shown in Figure 7.

A bearing element 30 is attached to the underside of the plate 16 by screws 31. The bearing element 3d is arcuate with its center of curvature at the axis 29, and While the bearing element extends for more than of arc, it does not cross the slots 21 and 22. ln the construction illustrated, the ends of the bearing element 3l) are at the guide surfaces of the slots 21 and 22. The bearing element 30 could be shorter, but it is preferably greaterV than 180 in order to provide a more adequate bearing.

The bearing element 3% has an undercut recess 33 around its outer portion, and there is a connecting plate 35 with an inner lip Vwhich ts the undercut recess 33';

VThe connecting plate 35 is secured to the forward channel 12 ofthe main frame.V The bearingr surfaces of theundercut recess 33 and the complementary lip of the connect-j ing plate 35 provide the bearing means on which the plate 16 is movable angularly aboutthe axes 2,9 asa center.

Referring againto Figure the guide plates 16 and 17 are connected togetherby a block 40which haS Screws Y 42, or similarV fastening means, connecting it with the Vrespective guide plates.` A lead screw'44 threads throughY Vthe bloclg 40, and the forward portion of the; lead screw Y. rotates in a thrust bearing 45 which prevents longitudinal movement of the lead screw. When a Wrench or handle is y applied to the forward Yend of the lead Screw 44 and theV Vlead screw is rotated, the: block. 40 is movedtoward or away from the thrust bearing 46'depending rection of rotation of the screw.`

A s the lead screw 44 is turned in a direction to pull. the blockV 40 toward the thrust bearing 45,'` the plate 116.1 isrotated 'clockwise about its axis 29, andtheV plate 17A is rotated connter-clocltwiseY about its axis `29. This movement in opposite directions effects the saineA adjustment for the guide Slots in both of the plates 16 and .17 because upon the di- 'Y the guide Slots are turned in opposite directions to com- ,Y

pensate for the fact that one operatesonra'right-hand Stringer and the otherron a leftfhand, Stringer. There are Scales`46-along outer arcuate edges of the plates 16 and '17 and these scales 46 move past indicators 47 on the This Stringer carrier 50 isa longvbeam, and preferably a pawl and ratchet mechanism illustrated, therefore, puts a minimum of lost motion into the driving mechanism of the machine. v

Referring again to Figure ,1, the pinion 75 meshes with a rack 78 extending from a piston rod 79 of a fluid-actuated motor 80. This motor 80 is secured to the front of the main frame 10 and has a bearingr82 in which the piston rod reciprocates. v

When thepistonyrodf79- moves toward ythe left in- Figure l, the'pinion 7 5 is lrotated counter-clockwise, and the shaft t 70 is rotated in the same direction through the pawl and ratchet mechanismen the-shaft70. When the. piston rod 79 moves toward the right, on its return stroke, the pinion 75 moves clockwise, but no rotation is imparted to the shaft 70 because the pawls of the ratchet mechanism move across the sloping faces of the ratchet teeth without turning the ratchet wheel.

There is a Slideway 84. fixedk to the` main frameand havingl an .undercut groove. 85 (Figure. la) by which the rack 78, is. supportedand invwhich the rack is freely slidableinlthefdirection of its. length. Thercvis a scale 86 l f which is also connected to the Vframe to indicate the strokechannel beam, so as to increase its rigidity. The Stringer or work piece 52 rests upon the Stringer carrier` 50,.` There is a Stringer holder 54;(Figure l) including a clamp 56,-for gripping the end of a Stringer.. The Stringerhol/derd 54;. hasa handle 57 which operates the clamp 56. Thestringer holder 54 is carried by a slide 60 which extends lenglhwise of the Stringer holder 54. l.

`Referring to Figure 2, there are grooves 6,2 in the con-V fronting top edges of the sides of'thestringer hold er5 4VV and these grooves provide atrackY along which the slide. 60 is movable to feed the Stringer 52v ,through-.themachine'.V On the bottomvface of theslide 6llltthere is `a rack64.

Referring, again to Figure l, the rack'` 64 mesheswith the teeth of a pinion 66when the slide 6l)l is to be-pmoved toward the right and mesheswithanother pinion 67V when Y Vthe slide iS to be moved toward vthe left. The rmschanism.v

for selectively'engaging thepinion 6,6,y or 6 7with therack. 64'will be described'in connectionrwith Figure 4.

The pinion 6,6 always meshes with the. Pinion 6.7' and. transmits rotary motion to the pinion 67 The. pinion..66. is driven by a gear 68 (Figure. 3) on ashaft 70., A ratchet.

' wheel 72 lis secured tothe Shaft '7,0-andisrotatedby pawls- 74 carried by a driving kpinion 75-,which isl also locatedon. the shaft 70fbut freely rotatable on the shaft.

The pawls 74k ar'econnected with the pinion, v'15b-y.. studs on which the pawls are free to swing in theusual manner, and all of the pawls have a biastoward-,the ratchet.. Wheel 72. The Studs kon which the pawls4 swing, are located so that when one pawl iSu in engagementwith the back of a tooth of the ratchet wheel, each successive.Y pawl around the ratchet wheel is progressiyelyifurther..fromthe back of the corresponding ratchet tooth in front; of thatv pawl. With this construction, there can: be very-littleL angular movement ofthe pinion 75 withrespectto; thev ratchet Wheel 72 without bringing one or another oft e*Y pawls 74 into positionto contact with thevback'of onei or the other of therteeth of the ratchet wheel72j. The

of @emptor- ,and rack 78. A lead screw .88y threads throughablock 9.41on the-front of the frame and carries an abutment 92 forflirnitingthe stroke of the`rnotor-80 and racl-78. The rack. 78 vcontacts with Vthe abutment 92 at the end of they stroke.,

By changing the setting .ofthe lead screw 88, theabiit-V ment,.`92zcan be shifted to any desired-position along the sc ale 86'so asvto obtain any.,pre-SelectedY strokefor the `The successiveoperations ofjthe motor S0 movethe,

stringerholder54, with la Step-byestep movement, and the` correct length yforeach step depends upon the correct rise for the stair stringerrwhichz is to .be routed by the, ma-

chine. Therproper` settings for the abutment 92, aswell Y as. the angularadjnstment ofthe guide plates 16/,and 17, are ytakenfrom aptablewhich shows different values and combinationsviof Y rise; and V runV with increments small.r enough to obtain any desired stair case. Y

ThereV--aretringer holders 5,4 at both'ends Iof thestringer.. carrier 50. When the Stringer isto be advanced through the machine toward-the right, the end of the Stringer isfplaced in the` clamp of the left-hand Stringer ho1d er 54; and when thev Stringer is `to be advanced through the machine toward' the left, the rearward endVV of thetstringer is placedin'the clamp` 56 of the-right-hand Stringer-1.holderV 54. Mechanism Yfor reversingthe direc.- tion,v of` travel of` the slideVVV 60,1 which; moves the VStringer holders 54,is best Shown in Figure4. The. gears 66.*and 67. rotate freely onshafts 96`and. 97 and 'are held againstA axialrnovement; on thesefshafts .by thrust collars 9S. The,

shafts 9.613131 97l lhemselvefare axially movable` in bear` ings-.9,9 carried byithevrnainY- frame When the gears-6,6. a1l1d--67fare-inl thefpositions'shown in FigureA 4, the gear.. 66rneshes lwiththe-racl; 64, bntthefgear; 67 is .beyondihe side of the raclg, Whenthejshaft 96 is moved' rear#z wardly, to carry the gear 66'. into thedotted line position shown-in Figure 4, the gearl 66 remains in mesh withV the driving gear 68, but moves beyond the side ofthe rackl 64-and out of mesh with the teeth of the rack. At the-Sametime that the gear 66 is moved rearwardly,- the gear 67 is moved forward into the dotted line position shown VinjFigure 4, and in the rack 64. o

This movementof the gears 66 and l67 is effectedV by a yoke elementlol which rocks about a vertical stud. 102,t and `whichyhas pins,1.03 engaging :circumferential grooves in the shafts 96 and 97. There is a handle105 108 (Figure 1v)V mounted on top of the guideplateslt16,.4

this positionl it meshes with` and 17. Each of these router tools 108 includes a motor 110 which 'nas a housing with a bottom ilange 112 that rests upon the guide plate 1&5 or 17. The bottom face of the ange 112 provides a bearing surface that slides on the top surface of the guide plate. There are handles 115 on both sides of the router tool 108 for moving it along the guiding edges of the slots in the guide plates.

Figure l0 illustrates the way in which each of the router tools S is guided to route one of the stringers 52. A cutter wheel 11S is attached to the lower end of the armature Shaft of the motor 110. Between the cutter wheel 118 and the bottom face of the flange 112, there is a guide roller 126 which contacts with the edge of the slot 22 to guide the cutter wheel 118 along a straight line. The router tool 103 is moved in one direction along the slot 22 with manual pressure exerted in a direction to hold the guide roller 120 against one side of the slot 22. After cutting to the end of the slot 22, the router tool 108 is moved in the opposite direction with manual pressure exerted to hold the guide roller 120 against the other side of the slot 22 So that the recess routed in the Stringer has the same width as the guide slot 22, less the difference in diameter of parts 118 and 126.

In order to hold the Stringer against movement while it is being routed, clamps are provided in the machine. The clamps are best shown in Figures 8. There is a clamping plate 125 located under the Stringer 52 in the region or" each of the connecting plates 35 which support the bearing means on which the guide plates are angularly adjustable. There is a spacer 132 on the bottom of the guide plate 17 which has a bottom face flush with the bottom face of the connecting plate 35.

The clamping plate 125 is connected to a piston rod 127 of a uid motor 128. The rearward end of the clamping plate 125 is supported by studs 129 which extend downwardly from the guide plate 17 and through holes in the clamping plate which are large enough to make the clamping plate 125 freely movable along the studs 129.

The motor 12S is supported on a cross brace 130 of the main frame of the machine. When working uid is supplied to the motor 128, the clamping plate 125, is pushed upwardly and this lifts the Stringer 52 from the Stringer carrier, and clamps the Stringer rmly against the bottom faces of the connecting plate 35 and spacer 132. By so clamping the Stringer after each advancing step, a uniform depth of the routed grooves is obtained.

A clamping jaw 135 is located above each of the clamping plates 125, and this clamping jaw 135 is connected to a piston rod 137 of a fluid-operated motor 138 which is secured to the main frame of the machine. When working fluid is supplied to the motor 138, to thrust the piston rod 137 toward the left in Figure 8, the clamping jaw 135 pushes the Stringer against an abutment 140 at the front of the machine. This abutment is adjustable, Within a limited range, toward and from the front frame channel 12, by lead screws 142 located near opposite ends of the abutment 140, as Shown in Figure 5. ln order to keep the abutment 140 in parallel positions when it is adjusted by the screws 142, these screws have sprockets 14S (Figure 1) connected to them, and the sprockets 143 are connected together by a chain 150 so that the sprockets are rotated in unison.

Referring again to Figure 8, there are one or more nozzles 155 located at the abutment 140 and facing in the direction of the Stringer 52. When each routing operation has been performed on the Stringer and the clamping plate 125 moves downwardly, to leave the Stringer free for its next step of advance, jets of compressed air are blown across the top surface of the Stringer from the nozzles S to remove all particles of wood which spill onto the top surface of the Stringer from the routed grooves or from the cutter wheels. This clearing of wood shavings from the top face of the Stringer prevents 6 the Stringer from being held out of contact with the bottom faces of the plate and spacer 132 when the plate 125 again moves upwardly into clamping position. Valves 156 control the air jets.

The sequence of operation of the machine is controlled by a crank 160 located at the front of a master control switch 162. This crank is movable into ve different positions indicated by the letters A, B, C, D and E (Figure 9) on the front of the switch housing. All of the valves for controlling the fluid-operated motors of the machine are preferably operated by solenoids, and are so illustrated in the drawing, though the invention can be made with mechanically operated valves.

Figures l1 and l2 are diagrammatic views showing the control apparatus for the machine. Figure 1l shows slide valve 166, for controlling the flow of working tluid to the motor S0. The slide valve 166 includes a casing 17d containing a valve element 172. There is a port in the valve casing 17) communicating with a conduit 172 which supplies air under pressure to the valve casing. There are two exhaust ports 174 opening through the valve casing 171) at spaced locations lengthwise of the valve casing. There is another port connected with a conduit which leads to the crank end of the motor 86; and another port communicating with a conduit 176 which leads to the head end of the cylinder 80.

The valve element 172 is urged toward the right in Figure ll by a spring 130. A magnetic stem 182, of the valve element 172, extends into a solenoid coil 184.

The spring urges the end of the valve 179 against an abutment 186 near one end of the valve casing. When the valve element 172 is against the abutment 186, the circumferential groove in the valve element puts the conduit 175 in communication with the pressure conduit 172 so that compressed air is supplied to the crank end of the motor 80 to operate the piston toward the iight; and the conduit 176 is in communication with the exhaust port 174.

When the solenoid 184 is energized, it moves the stem 182 and the valve element 172 toward the left, against the pressure of the spring 130 and into the position shown in Figure l1. This puts the the conduit 176 in communication with the pressure conduit 172; and connects the conduit 175 with the left-hand exhaust port 174 so that compressed air is supplied to the head end of the motor Sil to operate the piston rod 79 toward the left. This is the Working stroke of the motor which advances the Stringer through the machine by one step. Thus, energizing of the solenoid 184 causes the machine to advance the Stringer.

Figure 12 shows a Wiring diagram for the machine. Before explaining the circuits in Figure l2 reference should be made to Figure 8 which shows the feed motor Si?, the vertical clamping motor 123 and the horizontal clamping motor 13S. There is only one feed motor 80, but there are two vertical clamping motors 12S and two horizontal clamping motors 138. Both of the latter are shown in Figure 5 projecting beyond the back of the machine, and the vertical clamping motors 128 are indicated in dotted lines ahead of the horizontal clamping motors in Figure 5. In the preferred construction, all of these motors have solenoid-operated valves for admitting compressed air to their cylinders, and the solenoids are preferably controlled by relay switches; but, for purposes of simplifying the description, the relay coils in Figure l2 will be considered to be the solenoids which operate the valves.

The location of the coils in Figure 12 corresponds in orientation to the location of the iiuid motors in Figure 5. For example a coil 2111 operates the valve that controls the right hand vertical clamping motor 128 and a coil 202 operates the valve that controls the vertical left-hand clamping motor 123. Another coil 204 operates the valve that controls the right-hand horizontal clamping motor ans-,449

13S anda coil 205 operates the valve that controls the 5 left-hand horizontal clamping motor 138. The valve 166 which controls the feed motor Si), is operated by the soleswitches are normally open, that is they have `a bias toward open positionand they are closed when the coils are energized. Each of the switches 211, 212, 214 and 215 Y. Y

is connected in the circuitof its respective coil in such a way as to provide a stiel: circuit for maintaining the coil energized after it'has been momentarily energized by operation of a controller 217.

There is a Aswitch 220 associated with the coil 184.

This switch y220 is somewhat different from the other' switches in-that it has a spring 222 for holding the movable blade of the switch 220 in whatever position it was last shifted-to by energizing of the coil 184 o1'- a companion coil 224 which pulls the switch blade back against a-lixed stop 226-at a particular time in the operating cycle, as-Will-be more fully explainedin a later description of the operation of the circuit. Power is supplied to the switch 220 Vand the coil 134 from a transformer 2310Y which has its-primary winding connected to a source of power indicated by the reference character 231.

Power for operating, all of the other switches of the control mechanism is supplied from a separate transy former 235fwhich has its primary coil connected with a source of power indicated by the reference character 236. The circuit for one side of the secondary coil of the transformer 235 isthrough the frame of the machine, as indicated by the ground connection on the secondary coil of vthe transformer 235, and the ground connections on varv ious other circuits of the wiring diagram. The other side of the transformer 235 is connected with a selector switch 240 having a movable blade 241 which contacts selectively withiixed eontacs 244 and 245 on opposite sides of the switch 240. This switch 240 is operated by the handle 105 which reverses the direction ofjfeed of the machine.

When the reverse control handle 105 is in position to causethe machine to feed a Stringer in the direction which requires use of the right-hand guide plate 17 andthe righthand clamping motors 123 and 13S, the movable switchY one side ofthe transformer 230,' and is connected by a, conductor 253 to the lead screw 88 which adjusts thel W'hen the extension 84 is feed stroke of the machine. in contact with the abutment 92 on the end of the lead screw 88, a Y'circuit is completed from the contact arm 250, through the conductor 253 and lead screw 88, to the abutment -92 and then to the extension 85 which is grounded on the frame of the machine.

vThe abutment 92 is insulated from the lead screw 88' andv the conductor 253'is connected with this abutment through an opening in the lead screw with insulation around the conductor 253 to prevent it from being grounded on the lead screw and the block 90 through- Which the lead screw threads. The purpose of this ground connection through the abutment 92 and extension 84 is Y toypreventJany. of thecircuits, except the circuit which controls the -feed motor 80,17from being operated before the feed motor has completed its stroke and brought the extensiont841into contact with thev abutment 92.`

Thereis another coil 260-whi'ch operatesa switch 262. This switch 262lis-provided with a spring V263 lwhich normallyfholds theswitch 262i closed, and the switch-is opened when the coil-260V is energized, near the end of an operat-f ing cycle, for thepurpose ofreleasing allV of the stick circuits of the clampmotor operating-coils 201, 202, 204* t and 205. The operation of the control mechanism shown in Figure l2V is as follows:

The operatorV rst moves the contact arm 250 of the controller 217 into vpositionto touch the contact A. This closes a circuit from the transformer 230through the solenoid coil 184, through the conductor-265, contact A,

Contact arm 250 and through the conductor 251-back to the other side of the transformer 230.y When the coil 84 is energized, it attracts the movable arm of the switch-220 to a contact 267 which is connected with the conductor 265. This establishes a shunt circuit from the conductor l 265, through the switch 220 and through a conductor 269 back to the other'side of the transformer 230. This shunt circuit maintains the coil 184 Venergized after the circuit through the Contact arm 250 has been broken by `moving the contact arm 250 beyond thev contact A of theV controller217. v

With the coil 184-thus energized, the valveV 166 isoperatedv tosupplyrcompressed Vair to the motor 80 which moves the stringer'holder to advance thestringer for one step through therouting machine. At the end of the feed stroke of the motor 80,-the extension 84 of the feed mechanism is incontact with the abutment 92 and is held-in contact by the continued pressure of the working uid in the feed motor 80. The-operator next moves the contact arm 250 to the second contact Bon the controller 217.

This establishes a ground `circuit for the coils 204 and 205 which operate the valves that control the horizontal clamping motors. However, only-'one of the coils 204-and 20S is energized, depending uponthe position of the movable,` arm 241 ofthe selector switch 240. In the wiring diagram shown inFigure l2, the arm of the selector switch 240 is in contact with the fixed contact 245- andthis establishes a circuit from the transformer 235, through the selector switch 240, xed contact 245, coil 204 and throughv a conductor 271, contact B of the controller 217, contact arm 250, conductor 253,r abutment 92,` extension 84 and-then through the frame of the-machine back to the other side" of the transformer 235. Y

This energizing of the Vcoil 204 operates the valve to supply compressed air to the rightl hand clamping motor 138, and at the same time moves the switch arm 214 into position to touch a contact 272 andV establish a circuit through' a conductor 273-to a fixed contact 275 inthe switch 262A which is grounded on the frame. This shunt circuit keeps the coil 294 energizedafter the contact arm 250 is moved beyond thecontact B of the controller 217.V

The operator then moves the contact arm' 250 -to the third contact C 'and this establishes a circuit from the transformer 235, through the switch 240, xed contact 245, a' conductor 277, coil201, conductor 279, contact C, Contact arm V250'and thence through the conductor 253 to the frame of the machine as previously explained. This energizing ofthe coil Y20.1 moves the arm 211 into position to are now operated by compressed air and the partsof themachine are in position to perform therouting vstepon the Stringer'. After the routing step has been completed, thev operator moves they contact arm 250'into position to touchthe contact D of the controller 217. This energizes theY coil 224 through a conductor 282 which is always connectedl with the transformer 235 regardless of theposition ofthe selector switch 240'; The coil `224is grounded" through the contact D andthe Contact arm 250 t0 the conductor 253 which connects with the frame of the lmachine as previously described.

Energizing of the coil 224 rulls the blade of the switch 220 away from the coil 184 and into contact with the fixed abutment 226. This opens the circuit of the coil 184 and permits the valve 166 to return to its original position under pressure of the spring in the valve 166 as previously described. The direction of how of working uid to the feed motor 80 is reversed and the motor returns to its original position in preparation for another feed stroke.

The next step in the operation of the machine is to deenergize the coils 201 and 204 so that the valves which are operated by these coils will return to their normal positions, under inuence of spring bias of the Valve, and the clamps are thus released. This is accomplished by moving the contact arm 250 to position to touch the contact E of the controller 217. With the contact arm 25) on the contact E a circuit is closed from the transformer 230, through conductor 286, coil 260, conductor 287, contact E, contact arm 250, and back through the conductor 251 to the other side of the transformer 230. This energizing of the coil 260 opens the switch 262 and breaks the ground connection of both of the coils 201 and 2494 so that their switches 211 and 214 move into open position and leave the circuits of these coils 201 and 204 open even after the switch 262 closes again when the arm 250 is moved to the bottom, otf position Shown in Figure l2.

The preferred embodiment of this invention has been illustrated and described, but changes and modications can be made and some features can be used alone or in different combinations without departing from the invention as defined in the claims.

I claim aS my invention:

l. A machine for routing stair stringere including a xed frame, a Stringer carrier movable through the xed frame, a router guideplate having two intersecting guide slots therein corresponding to the riser and tread of the stairs, the guideplate being located on the frame above the Stringer carrier, bearing means oy which the guideplate is attached to the frame at a relatively ixed location on said frame and about which the guideplate is rotatable about a center near the intersection of the guide slots in the plate to change the ratio of rise to run for the stringers routed by the machine, feed mechanism for advancing the Stringer carrier with a Step-by-step movement past the guideplate, and adjustable means for changing the length of the Steps of the feed mechanism m accordance with the position of the guideplate to adjust the machine for stair stringers having dierent ratios of rise to run.

2. A Stair Stringer routing machine comprising a fixed frame, a Stringer carrier extending through the iixed frame and movable longitudinally with respect to the xed frame, reversible mechanism for feeding the Stringer carrier in opposite directions with a Step-by-step movement, two guideplates supported by the frame and located above the Stringer carrier, the guideplates having slots therein through which a router extends with a side of each guide Slot serving as a guide for controlling the path followed by the router, each of the plates having two intersecting guide Slots, one for the riser channel and the other for the tread channel of the stringers, and one of the plates having the guide slots in position for a right-hand Stringer while the other guideplate has the slots in position for a corresponding left-hand Stringer, beming means on which the guideplates are movable to change the angular positions of the guide slots with respect to the longitudinal edges of a Stringer on the carrier to change the ratio of the rise and run of the channels routed by the machine, and means for adjusting the feed mechanism to accommodate the rise-run ratio for which the guideplates are adjusted.

3. A stair Stringer routing machine including a fixed frame, a Stringer carrier movable lengthwise through the fixed frame, a guideplate supported by the frame and having intersecting slots for guiding a router which cuts' channel for the riser and a channel for the tread, both of the guide slots extending beyond one margin of a Stringer supported on the carrier, bearing means on which the plate is rotatable to change the ratio of the riser channel length to the tread channel length, an adjusting screw for rotating the plate on the bearing means, a scale and indicator, one of which is on the plate and the other on the frame, for measuring the angular position of the plate, feed mechanism that advances the carrier with a Step-by-step movement, and means for adjusting the feed mechanism to co-ordinate the length of each step with the angular adjustment of the guideplate.

4. The stair Stringer routing machine described in claim 3 and in which the feed mechanism includes a reciprocat-` ing uid motor and motion-transmitting connections between the fluid motor and the Stringer carrier for imparting the step-by-step movement to the Stringer carrier.

5. The stair Stringer routing machine described in claim 3 and in which the feed mechanism includes a reciprocating uid motor, and motion-transmitting connections between the motor and the Stringer carrier, said connections including a rack operated by the uid motor, a pinion that meshes with the rack, another rack carried by the Stringer carrier, a pinion that meshes with the Stringer carrier rack, and gearing between the pinions including means for reversing the direction of rotation of one pinion with respect to the other when the Stringer carrier is to be fed in an opposite direction.

6. A Stair Stringer routing machine including a frame, a Stringer carrier movable lengthwise with respect to the frame, a plate supported by the frame and having a piurality of guide slots therethrough for guiding a routing tool, the guide Slots being correlated for producing a riser channel and a tread channel for a right-hand Stringer, another guideplate supported by the frame and having slots therein for guiding a router tool to produce a riser channel and a tread channel for a left-hand Stringer, the guide Slots extending beyond one edge of the Stringer on the carrier, bearing means on which each of the guideplates is movable to change the angles of the guide Slots with respect to the edge of the Stringer to change the rise-run ratio of the Stringer, common adjustment means connected with both of the guideplates for adjusting the plates in unison, indicators for designating the angular positions of the guideplates, feed mechanism that produces step-by-step relative movement of the Stringer carrier and frame, and means for adjusting the feed mechanism to change the length of the steps in accordance with the angular setting of the guideplates.

7. A stair Stringer routing machine including a frame, a stair Stringer holder, Step-by-step feed mechanism for producing relative movement of the holder and frame, a plate supported by the frame above the Stringer and having router guide Slots therein including one for a riser channel and another for a tread channel, a clamping face beneath the plate and above a Stringer on said holder, a clamping jaw beneath the Stringer, operating mechanism that moves the clamping jaw toward the level of the clamping face to clamp the Stringer against Said clamping face prior to each routing operation, said operating mechanism being movable into position to release the clamping pressure prior to the operation of the feed mechanism after each routing operation, and bearing means on which the plate is rotatable to change the ratio of the riser channel length to the tread channel length.

8. A stair Stringer routing machine including a main frame, a Stringer holder, feed mechanism that advances the Stringer holder in a direction longitudinally of the frame and past a router Station on the main frame with a step-by-Step movement, a guideplate connected to the frame at the router Station and Supported by said frame at a location above the Stringer, guide slots in the plate at substantially right angles to one another for extending beyond one longitudinal edge of the Stringer on the 1 1 holder, bearingl means onf-Which the guideplate is rotatable withrespectV to the frameto' 'changethe' riserun ratioV of they Stringer, a clamping face on theframe, and clamping means carried by the frame in position to exert a clamping `pressure against the Stringer in ak direction i transverse of the Stringer and towardsaicl clamping'faceV to clamp the Stringer against said face prior to each routv ing operation, and control means operable torelease the clamping means prior to each'operation of the Step-bystep feed mechanisnr at a location'near the slots in the plate. Y t

V9. VThe stair Stringer routing machine describedV in claim 8, and in which there are other clamping means located beneath the Stringer and operable to thrust the Stringer upwardlyagainst a face ofthe frame;

l0.v A stair Stringer routing machine/including ak frame,

a Stringer holder, feed means that produce relative stepby-step movement of 'the Stringer holder and frame in a direction longitudinally of the' holder, two guideplates supported by the frame andconnected'with bearing means on which the guideplates are movable intoV dierent angular positions in a plane parallel to the stringer'face in which channels are to be routed, guide slotsin the plates for guiding a router* tool to cut channels in the stringers,

I the guide Slots in one plate being correlatedffor a righthand Stringer and the guide slots inthe other plate'being correlated for a left-hand Stringer, clamping means' for holding a Stringer in position during a routing operation, the clamping means including separate power clamps for each of the guideplates, ra controller for the clamps, and selector mechanism n alternately 'connecting one or the other of the clamps with the controller,

ll. A stair Stringer routing machine'including a frame,

y a Stringer holder, feed mechanism'that produces step-bysteprelative motiony of'ethel Stringer holder andframeI inv a direction lengthwise of the frame, a guideplate carried:

by the frame with slots therein for guiding a router tool toy cut a riser channel and a tread channel in a face of the" Stringer, bearing means4 on which the plate is movable which the Stringer is held by the clamps at locations-in the regionof'the guide Slots,-poWer actuating means' for the clamps, a controller, andswitch means-operated by the controller for controlling the actuating-means ofi-thevr clamps,

l2. The stair Stringer routing machine describedin claim ll and in which the'power actuating means include reciprocating fluid motors, and in which the feedY mechanism includes a reciprocating luid motor, and the' controller has a group of separate Switches which are successively operated to supply working uid to the feed motor first and'then to the clamping motors.

References Cited inthe le of this patent UNITED STATES PATENTS 1,306,252 Dauger June l0, 1919' i,75l,8l6 Hunter s Mar.v 25, 19,30

1,808;962 Mackay .Tune 9, 1931k FOREIGN PATENTS 278,408 Great Britain ocr. 11, 1927 to a longitudinal edge of' 

